Ground based and airborne in-situ Measurements of volcanic Carbon and Sulfur Emissions at high temporal Resolution

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This is a request for travel funds for a trip from Germany to GNS and the White Island Volcano in New Zealand, where we plan in-situ measurements of volcanic SO2 with a new type of instrument together with researchers from NZ. Combined with in-situ CO2 measurements we expect a data set of CO2/SO2 ratios of unprecedented accuracy and time resolution.Although remote sensing of SO2 has become well established among volcanologists over the last decades, ground based and airborne in-situ-measurements remain essential to obtain comple¬mentary information. Nowadays in-situ measurements of SO2 are often performed by electrochemical sensors, which suffer from several disadvantages including (1) relatively long response times (ca. 20 s and more), (2) interferences to several other reactive gas species present in volcanic plumes (which are hard to quantify or even unknown), (3) the need for frequent calibration. We overcome these problems with a newly developed optical in-situ SO2-sensor prototype, relying on the principle of non-dispersive UV-absorption (PITSA, Portable in-situ Sulfurdioxide Analyser). Its cost-effective application for measurements of SO2 has become possible by the recent developments of UV-LEDs. The sample air is pumped through a glass cell, where it is exposed to the light beam of an UV-LED (ca. 290nm), in which essentially only SO2 shows absorption features. Therefore the reduction of the radiation intensity passing the cell becomes an indicator for the sample air's SO2-content. The PITSA device is combined with a commercial CO2 sensor using its infrastructure (pump, microprocessor, power supply, p, T-sensors) thus allowing SO2 and CO2 measurements at 0.1 ppm and 1 ppm accuracy, respectively. This allows new volcanological applications.